Cryogenic heat station and apparatus incorporating the same

ABSTRACT

An improved heat station for cryogenic apparatus comprising one or more narrow fluid passages in heat exchange relationship with a portion of the external walls which enclose a refrigeration chamber of variable volume. The narrow fluid passages provide an extension of the fluid flow path of the apparatus which in turn provides an increase in heat transfer surface without any appreciable increase in void volume.

United States Patent lnventon Fred F. Che!!! Mlncheeter; Jane: A. O'Nel,Bedtord, both of, Mass. Appl. No. 807,606 Filed Mar. 17, 1969 PatentedAug. 24, 197] Aleignee Cryogenic Technology, Inc.

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62/6 F25b9/00 FleldolSeerch 62/6 so 90 as so as as as or L- as asPrimary Examiner William J. Wye AnomeyBessie A Lepper ABSTRACT: Animproved heat station for cryogenic apparatus comprising one or morenarrow fluid passages in heat exchange relationship with a portion ofthe external walls which enclose a refrigeration chamber of variablevolume. The narrow fluid passages provide an extension of the fluid flowpath of the apparatus which in turn provides an increase in heattransfer surface without any appreciable increase in void volume.

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Attorney PATENIED M1824 m1 SHEU 3 OF 4 1 I I I u 0 Fred F. Chellis JamesA. O'Neil IN VENTORS PATENIEU/msumn I 3600,9023

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Fred F. Chellis James A. O'Neil INVENTORS Attorney CRYOGENIC HEATSTATION AND APPARATUS INCORPORATING THE SAME This invention relates torefrigerators and liquiflers and, more particularly, to cryogenicapparatus which develop refrigeration through the expansion of acompressed fluid and which may incorporate one or more regenerators.

The refrigeration in such apparatus is typically delivered to a loadthrough a suitable thermal connection which is generally referred to asa heat station. Refrigerators to which the heat station of thisinvention may be applied include those described in U.S. Pat. Nos.2,906,10l, 2,966,035, 3,188,819, 3,2 I 8,8 l S, the well-known Stirlingcycle refrigerators, and any other type of cryogenic device which has amoving fluid stream passing through a refrigerating chamber. As examplesof the types of refrigerators in which the improved heat station of thisinvention is designed to be incorporated, we may cite the refrigeratorsshown in U.S. Pat. No. 3,218,815. Thus, heat station 28 of FIGS. 1 and4, 85 of FIG. 6 and FIG. 9, 135 of FIG. l0, and 218 and 220 ofFlG. 12 ofUSP 3,218,815 may be constructed in accordance with this invention. Itwill be seen that in each of the types of apparatus mentioned thecryogenic refrigerator is of a type in which a movable member defineswithin an enclosure at least one refrigeration chamber of variablevolume, and in which a high pressure expansible fluid is introducedthrough a fluid flow path which may incorporate heat storage means aspart of the path. The fluid flow path normally terminates in therefrigeration chamber wherein the fluid is subsequently expanded andthen discharged through the same fluid flow path.

Refrigeration from this moving fluid stream is delivered to an externalload through the refrigerator housing, the heat sta tion walls, or acombination of these heat flow paths. In coupling the external load tothe moving fluid stream it is highly desirable to provide as much heattransfer surface as is possible. However, in order to make the mosteffective use of the refrigeration in the fluid, it is also necessary tomaintain the void volume as low as possible.

It is, therefore, a primary object of this invention to provide animproved cryogenic heat station of the type which achieves an improvedtransfer of heat between a fluid stream and an external load. It isanother object of this invention to provide a heat station of thecharacter described which achieves the use of a maximum surface areawhile at the same time maintaining the void volume at a minimum. It isyet another object of this invention to provide a heat station of thecharacter described which is applicable to various refrigeration cycleswhich involve the expansion of high pressure fluid to achieverefrigeration. It is another object of this invention to provide animproved cryogenic apparatus which incorporates a heat station. Otherobjects of the invention will, in part, be obvious and will, in part, beapparent hereinafter.

The heat station of this invention may be generally described ascomprising means, external of that portion of the apparatus enclosurehousing defining the cold or refrigerating chamber, for defining one ormore narrow fluid passages which provide indirect fluid communicationbetween the fluid flow path of the apparatus and the refrigeratingchamber. The fluid passage or passages may in heat exchange relationshipwith a portion or essentially all of the external walls defining therefrigerating chambers and valve means may be added to control the flowof fluid through the passage or passages within the heat station.

The invention accordingly comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claimsv For a fullerunderstanding of the nature and objects of the invention, referenceshould be had to the following detailed description taken in connectionwith the accompanying drawings in which FIG. 1 is a longitudinal crosssection of a single'stage cryogenic refrigerator constructed with oneembodiment of the heat station of this invention;

FIG. la is a modification of the heat station embodiment of FIG. 1;

FIG. 2 is a cross section of the heat station taken along line 22 ofFIG. 1;

FIG. 3 is a modification of a portion of the refrigerator and heatstation of FIG. 1 showing the use of one-way check valves to modify thefluid flow path within the refrigerator;

FIG. 4 shows the heat station of FIG. I associated with a refrigeratorhaving an external regenerator;

FIG. 5 illustrates another embodiment of the heat station having asingle annular passage;

FIG. 6 is a cross section of another embodiment of the heat station ofthis invention;

FIG. 7 is a longitudinal cross section of a multiple stage refrigeratorshowing the heat station of this invention affixed to an intermediatestage; and

FIG. 8 is a diagrammatic representation of a complete cryogenicapparatus incorporating a multistage refrigerator having the heatstations of this invention coupled to heat exchangers in a Joule-Thomsonloop.

The heat station of this invention is shown in FIG. I incorporated in acryogenic refrigerator which embodies the cycle disclosed in U.S. Pat.No. 2,966,035. In this particular embodiment there is but onerefrigeration chamber. It will be shown in FIG. 7 that the heat stationof this invention may be used with one or more cold chambers of atemperature-staged cryogenic refrigerator such as described in U.S. PatvNo. 2,966,035.

The refrigerator of FIG. 1 is seen to be comprised ofa cylindricalhousing section 10 which is attached to a mounting plate 11 forconnection with a crosshead l2. Sealing of the crosshead to the plate isaccomplished through an O-ring I3. The heat station of this invention isshown generally at numeral I5 and a thermal load at 16.

Within the housing section 10 there is a movable member, such as adisplacer 20, which in its movement defines a warm volume 21 at one endof the housing section and a cold volume 22 at the other end. Thedisplacer 20 is attached to a displacer shaft 24 and in keeping withdisplacer design it has an upper sealing means which comprises anelastomeric ring 25 and a polytetrafluorethylene member 26, as well asan upper land 27 and a lower land 28 which makes sealing contact withthe internal walls of the housing 10. Fluid is introduced into therefrigerator and is withdrawn from the refrigerator by means ofa passage(not shown) in header 14. The fluid flow path within the refrigeratorcomprises the warm chamber 21, a first vertical passage 30 within thedisplacer, an upper plenum chamber 31, a regenerator 32, a lower plenumchamber 33, a lower or second vertical passage 34, the heat station 15(to be described in detail) and finally the refrigeration chamber 22.The regenerator 32 terminates at its upper end in a perforated plate 36and in its lower end in a perforated plate 37 which retains theregenerator material such as lead balls, screening or wire within thevolume of the regeneratorv The displacer 20 terminates at its bottom endin a clamp plate 42 which is attached to the bottom solid portion 43 ofthe displacer by means ofsuitable screws 44.

It will be appreciated by those skilled in the art that the displacermay be replaced by a piston such as in a Stirling engine, and the mannerin which such a movable member forms sealing contact with the internalwalls ofthe housing may be of a variety of designs and constructions.Therefore, the embodiment illustrated in FIG. I is not limiting.Moreover, in the description given the terms upper" and lower are usedin a relative sense, and the refrigeration apparatus illustrated may beoriented in any manner. These terms are employed in this descriptiononly for convenience and to correspond to the orientation illustrated inthe figures.

Affixed to the bottom end of the housing section is a heavy wall supportplate 48 which in effect serves as part of the enclosure housing andwhich is formed integral with a passage-defining extension 49 having afluid passage 50 which communicates with the second or lower verticalfluid passage 34 of the solid displacer section 43.

ln its upward and downward motions, the displacer slides on the passagedefining extension 49, the outer wall of which has a sufficiently smoothfinish to make a seal with the fluidsealing means which is representedgenerally at 54 and which is located just above a central opening 53 inthe clamp plate 42. The fluid-sealing means 54 may be made up of one ofa number of different types of seal components, the one illustrated inFIG. 1 comprising a sealing ring 55 formed of polytetrafluorethylene, aseal backup ring 56, a spacer washer 58, and finally a Bellville springwasher 59.

The fluid passage 50 which furnishes direct fluid communi cation withthe regenerator terminates in a very narrow or shallow, generallycircularly shaped passage 65 defined between the bottom wall of thesupport plate 48 (serving as the end of the housing section whichdefines the refrigeration chamber 22) and the top wall of a copper plate66. The copper plate is affixed to the support plate 48 inspace-defining relationship by a plurality of screws 67 and spacerwashers 68. By means of this shallow, essentially circularly shapedpassage, the fluid is forced to flow beneath the chamber 22.

Positioned around the refrigerator wall are a plurality of annular rings70 and 71 formed of a material which has good heat conductivity at thetemperature at which the refrigerator is to deliver refrigeration. Forcryogenic purposes these rings are preferably formed of copper.Surrounding and spaced from the outermost one of these rings is acylindrical heat station housing 73 formed of a material which has thenecessary strength at cryogenic temperatures to support the housing.Typically the housing 73 and the support plate 48 with its integralextension passage-defining means 49 will be formed of stainless steel.An annular ring of stainless steel 74 is welded between the outside wallof housing 10 and the inner wall of the heat station housing 73 to forma fluidtight sea]. It is so positioned as to define a narrow fluid flowpath 75 between it and the uppermost edges of rings 70 and 71. Alongtheir lower edges the rings 70 and 71 are joined to each other and tothe copper plate 66 with a thermal bond 76; while the heat stationhousing 73 is welded with a strength bond 77 to the copper plate 66.

The annular rings 70 and 71 are maintained in their spaced relationshipwithin the heat station housing by means of a series of spacers 80, 81and 82 (see also FIG. 2). There is, therefore, defined between the outerwall of refrigerator housing 10, the spacer rings 70 and 71 and the heatstation housing wall 73 a series of annular fluid passageways, 85, 86and 87. Communication with these passageways from the narrow fluidpassage 65 is by way of openings 88 and 89 cut in the bottom section ofthe annular rings 70 and 7| (see also FIG. 2). There is also supplied ameans for fluid communication between these annular fluid passages 85,86 and 87 and the interior of the refrigeration chamber 22, this meansbeing a series of ports 90 drilled in the refrigerator housing below theposition of the annular ring 74 but fairly close to the top of the rings70 and 71.

The particular refrigerator embodiment of FIG. I operates on a cycle inwhich a predetermined quantity of high pressure fluid is introduced byway of the regenerator into the refrigeration chamber 22. As the highpressure fluid passes down through the regenerator 32 it is cooledinitially and reaches the refrigeration chamber 22 as high pressure,initially cooled fluid. Subsequently, the supply of high pressure fluidis cut off and the system is opened to a low pressure exhaust reservoirat which point the cold, high pressure fluid expands, is further cooledand gives out refrigeration to the regenerator 32 as it leaves therefrigerator.

in the heat station of this invention, the flow path of the highpressure, initially cooled fluid is so modified as to cause it to comeinto contact with a much enlarged heat transfer surface while at thesame time maintaining the void volume within the refrigerator at aminimum. The void volume is, of course, comprised of that space which isrequired for clearances and gas passage purposes and which does notcontribute to the development of refrigeration through the expansion ofthe high pressure gas. Thus in the heat station of this invention heattransfer is maximized without appreciably reducing the efficiency of theapparatus through increase in void volume.

From the regenerator the fluid passes down through the vertical passage34 and into the passage 50. It is therefore forced through the narrowhorizontal fluid passage 65 into the spaced ring system, a portion of itflowing upwardly through annular channel 85, a portion through annularchannel 86, and a third portion through annular channel 87, theseportions being divided and routed at the bottom end of the refrigeratorand passing through the openings 88 and 89. All of the fluid which haspassed up through the annular channels 85, 86 and 87 is then collectedin passage 75 and enters the refrigeration chamber 22 through the seriesof ports 90.

In the embodiment of the refrigerator of FIG. 1, after the system hasbeen opened to the low pressure reservoir side of the cycle, thedisplacer moves downwardly and forces the fluid back through the sameflow path by which it entered the refrigeration chamber 22.

In the modification of FIG. la, in which like numerals refer to likeelements of FIG. 1, a second copper plate 67 is bolted by means of aplurality of screws 69 to copper plate 66. Copper plate 66 has acircular shallow well 91 machined in it, the well being open torefrigeration chamber 22 through a number of passages 92 drilled throughthe plate. A circular disk 93 is affixed to the end of passage-definingextension 49 and is located within shallow well 91 to define with it andthe surface of copper plate 67 a narrow fluid flow path comprisingcircular passage 94, which is in direct fluid communication with theregenerator through fluid passage 50, and annular passage 95 which is indirect fluid communication with refrigeration chamber 22 throughpassages 92. If desired a centrally located recess 96 may be drilled inplate 67 better to direct the fluid out through circular passage 94.Finally, a plurality of external conduits 97 may be used with or withoutpassages 92 to provide fluid communication between annular passage 95and refrigeration chamber 22. A plurality of thermal connecting members98 provide a heat transfer path among the heat station components.

Under some conditions of operation, it may be desirable to transfer thehigh pressure incoming fluid directly from the regenerator to therefrigeration chamber 22. A modification of the refrigerator and heatstation flow path which accomplishes this is shown in FIG. 3. In thismodification, there is provided in the solid bottom section 43 of thedisplacer an additional fluid channel 100 which has in it a one-wayfluid check valve 101, the embodiment shown in FIG. 3 being formed of aball 102 and a spring 103. Since there will, of course, be someresistance to the fluid flow through valve 101, some of the highpressure fluid will also flow into passage 50 and through the heatstation, unless means are provided to check the fluid flow by thisroute. Therefore, the passagedefining extension 49 may be modified tohave an upper inwardly directed flange 104 and an annular ring 105 tohold another one-way check valve 106, shown in FIG. 3, to comprise aball 107 and spring 108.

In operation, when the high pressure fluid is being introduced into therefrigeration chamber prior to expansion but subsequent to the initialcooling in the regenerator, the fluid flows down through channel 100directly into chamber 22. However, during discharge the cold fluidcannot flow upward through channel 100 because the valve constructiondoes not permit it to be returned directly into the regenerator.Therefore, the discharging fluid must flow through the flow pathindicated in FIG. 1, that is outward through ports 90, then through theannular channels 85, 86 and 87 through ports 88 and 89, fluid channel 65and then through the fluid passage 50 and valve 106 to be returned tothe regenerator 32.

As illustrated in FIG. 4, the regenerator may be located external of thehousing section 10, an arrangement which is equally adaptable to singleor multiple stage devices. In the apparatus of FIG. 4 (showing the heatstation of this invention incorporated into one of the embodiments ofU.S. Pat. No. 2,906,]l or 2,966,035), in which like numerals refer tolike elements of FIG. I of the drawings presented herein, the displacer115 does not provide any part of the fluid flow path. A regenerator I16,located externally of the housing section, is connected to the fluidpassage 65 through an external conduit I17 and a passage 1 I8 drilled inthe copper plate 66.

It is, of course, within the scope of this invention to construct theheat station with one or more annular rings and FIG. illustrates anotherembodiment of the heat station in which a single annular passageway isprovided around the side of the refrigeration chamber 22 and directfluid communication is provided between the narrow horizontal fluidpassage below the refrigeration chamber and the interior volume of therefrigeration chamber. In FIG. 5 like reference numbers are used toidentify like elements as shown in FIG. I.

In the embodiment of FIG. 5 the refrigeration chamber 22 is closed onthe bottom by a cap 120 which extends upwardly to encase that part ofthe housing section 10 which is enclosed within the heat station housingI21 formed ofa material, e.g., copper, having good heat conductivity atthe cryogenic temperatures involved. The cap I provides the bottom wallfor the enclosure housing and is typically formed of copper. Cap I20 hasa fluid port 122 which provides fluid communication with the veryshallow, circular-shaped horizontal chamber 123 and a plurality of fluidports I24 which are aligned with ports 90 in the housing 10. An annularfluid passage I25 connects the shallow chamber 123 to ports 124 andports 90, and a plurality of thermal connecting members I26 provide adirect heat transfer path between cap 120 and housing I2].

Regenerator 32 is connected at its lower end to a plurality of radialpassages I28 which open into a narrow annular passageway I29 definedbetween the outer wall of the lower displacer section 43 and the innerwall of housing 10. This passageway 129 provides continuous fluidcommunication between the regenerator and passage I25 (by way of ports90 and I24) throughout the entire travel distance of the displacer. Aseal 130 prevents any direct fluid communication between the regeneratorand the refrigeration chamber 22. The embodiment of FIG. 5 may beconstructed as in FIG. I to have additional copper rings and spacerslocated between the annular extension of cap 120 and the heat stationhousing 121, thereby to provide additional heat transfer surface.

In the embodiments of FIGS. 1-5 (except for FIG. la the heat station ispositioned to surround the refrigerator housing and extends up to aboutthe point which corresponds to the maximum volume of refrigerationchamber 22. Although it is preferable for the heat station to occupythis position and relationship with respect to the refrigeration chamberand housing, it is possible for the heat station to extend either beyondthe height of displacer travel or to extend over only a portion of thisdistance; and it is also possible in apparatus housing the regeneratorin the displacer to provide a heat station which extends only over avery short length of the housing and has an extension beyond the housingas shown in FIG. 6.

The heat station of FIG. 6 comprises a fluid passage around housing I0in the form of a manifold I35, which communicates with annular passageI29 through a plurality of ports 90, and a small diameter tubing I36which connects manifold I35 with chamber 22. Tubing 136 is adapted toextend the passage and to deliver refrigeration to a load I37, and itmay comprise one or more parallel tubings corresponding in function tothe one or more annular passages (cg, 85, 86 and 87 of FIGS. I and 3 orI25 of FIG. 5) and to the narrow horizontal passage (e.g.. 65 of FIG. Ior I26 of FIG. 5). The sealing member I prevents direct fluidcommunication between the annular passage I29 and refrigeration chamber22 and forces the fluid to flow through the small diameter tubing I36which is typically formed of copper.

It is, of course, to be understood that at least the colder end of thecryogenic apparatus is to be suitably insulated and that the heatstation (whether attached to the housing or positioned as in FIG. 6)will be protected by such thermal insulation.

The embodiments of FIGS. 1, 3, 4 and 5 will be seen to include one ormore narrow fluid passages essentially surrounding all of that portionof the housing wall corresponding to the maximum volume of the chamber22. In FIGS. I, 3 and 4 there are a plurality of annular passages whilein FIG. 5 there is a single annular passage. In FIG. Ia passages arelimited to those associated with the bottom end of the housing and theseveral external connecting conduits 97.

FIG. 7 illustrates the application of the heat station of this inventionto a multistate refrigerator or liquifier. The colder or lower stage isconstructed as shown in cross section in FIG. I in which like numbersrefer to like elements. In adapting the heat station to an intermediaterefrigeration stage, it is necessary, as in the embodiment of FIG. 5, toprovide for continuous fluid communication between the regenerator andthe heat station passages during the entire stroke of the displacer.

The main refrigerator housing comprises an upper section I45 and a lowersection I46; and the displacer likewise comprises an upper section 147and lower section 148, each section containing a regenerator I49 andI50. High pressure fluid is introduced into the upper chamber 21 throughline 152 and low pressure fluid discharged through line 153. Fluidpassage 154 connects chamber 2I with regenerator 149 and fluid passage155 connects regenerators I49 and 150. A portion of the high pressurefluid which passes through regenerator I49 enters the firstrefrigeration chamber I56 through heat station 157 while the remainderenters regenerator 150 for passage through heat station 15 to enter thecolder refrigeration chamber 22 (FIG. 1).

Heat station 157 is formed ofa housing I58, a heavy copper bottom wallI59, the lower portion of refrigerator housing I45, a plurality ofannular copper rings I6I and I62, and spacers I63, I64 and I65. The flowpath joining regenerator I49 and refrigeration chamber I56 thereforecomprises passageway 155, radial passages I70, the shallow circularpassage 171, ports I72 and 173, annular passages I70, the shallowcircular passage 17], ports I72 and I73, annular passages 174, I75 and176, upper passage I77, and finally ports 178. As the displacer movesdownwardly, sealing ring serves as a means to terminate an annularpassage I81 between the lower displacer section I48 and lower housingsection I46. This passage I81 maintains fluid communication betweenradial passages I70 and circular passage I7I throughout the displacertravel. Sealing ring 182 prevents any direct fluid communication betweenpassage I71 and chamber 156.

FIG. 8 is a diagrammatic representation of a cryogenic apparatus 192(refrigerator or liquifier) incorporating heat stations of thisinvention used to cool a fluid circulating in a Joule-Thomson loop 193.The cryogenic apparatus as shown is constructed in three stages 194, 195and I96, each succeeding stage delivering refrigeration at a lowertemperature through heat stations 197, I98 and I99. In the modificationillustrated, the same fluid is used in both the cryogenic ap paratus I92and the Joule-Thomson loop I93, an arrangement which permits the use ofa single high pressure fluid source 200 and low pressure dischargereservoir 201. If desirable, a compressor 202 is incorporated in thefluid line between the high pressure and low pressure sides. It is, ofcourse, within the scope of this disclosure to use separate fluids inthe refrigerator I92 and in the Joule-Thomson loop I93, in which caseseparate high pressure fluid sources and low pressure fluid reservoirswould be provided. The high pressure line 205 in the Joule-Thomson looppasses through heat exchangers 206, 207 and 208 for indirect heatexchange with the cold fluid in heat stations I97, 198 and 199 and thenthrough Joule-Thomson heat exchanger 209 prior to expansion in aJoule-Thomson valve 210. The finally cooled fluid (partially liquefiedif desired) is discharged into reservoir 21] and at least a portion ofit is returned as cold low pressure gas through the low pressure side212 of the Joule-Thomson loop where it is used to indirectly precool thehigh pressure fluid in heat exchangers 209, 215, 216 and 217.

It will be seen that by providing the unique flow path in the heatstation, it is possible to obtain more effective transfer of heatbetween the moving fluid stream and the components of the heat stationwhich, in turn, are used to transfer the heat to a load. such as a maseror infrared detection device or to fluid in a Joule-Thomson loop. Sincethere is no material increase in the size or void volume, it will beseen that it is possible to obtain improved heat transferability withinessentially the same structure of the system. in summary therefore, itis possible to couple a heat load to a moving gas stream and obtain themaximum refrigeration at a minimum temperature penalty.

We claim:

1. in a cryogenic apparatus in which a refrigerating chamber of variablevolume is defined within a fluid tight enclosure housing and is in fluidcommunication with a fluid flow path in which a fluid stream iscirculated, a heat station adapted to effect indirect heat transferbetween at least a portion of said fluid stream circulating in saidfluid flow path and an external load and comprising means external ofsaid enclosure housing defining narrow fluid passage means around atleast a portion of said refrigerating chamber, said narrow fluid passagemeans within said heat station providing fluid communication betweensaid fluid flow path and said refrigerating chamber.

2. A cryogenic apparatus in accordance with claim 1 wherein said narrowfluid passage means comprises a fluid passage associated with the end ofsaid enclosure housing.

3. A cryogenic apparatus in accordance with claim 1 wherein said narrowfluid passage means comprises at least one annular passage around saidenclosure housing.

4. A cryogenic apparatus in accordance with claim I wherein said narrowfluid passage means comprises a fluid passage associated with the end ofsaid enclosure housing and a plurality of concentric connected fluidpassages around the side of said enclosure housing.

5. A cryogenic apparatus in accordance with claim I furthercharacterized by having fluid communication means providing a directfluid connection between said fluid flow path and said refrigerationchamber and having fluid flow control means.

6. A cryogenic apparatus in which a movable member defines within anenclosure a chamber of variable volume and in which a high pressureexpansible fluid is introduced through a fluid flow path into saidchamber and then discharged into a low pressure reservoir through saidflow path, said flow path incorporating heat storage means as anintegral part thereof; said flow path being characterized as includingheat station means comprising means external of said enclosure definingnarrow fluid passage means around at least a portion of saidrefrigerating chamber, said narrow fluid passage means providing atleast a portion of a fluid connection between said heat storage meansand said refrigeration chamber.

7. A cryogenic apparatus in accordance with claim 5 wherein said heatstorage means is located within said movable member.

8. A cryogenic apparatus in accordance with claim 7 furthercharacterized by having a fluid channel incorporating check valve meansadapted to provide direct fluid communication between said heat storagemeans and said chamber for high pressure fluid entering said chamber.

9. A cryogenic apparatus in which a movable member defines within oneend of a cylindrical enclosure a chamber of variable volume and in whicha high pressure expansible fluid is introduced through a fluid flow pathinto said chamber to be expanded and then discharged through said flowpath, said flow path incorporating heat storage means as an integralpart thereof, and including heat station means, said heat station meanscomprising in combination a. a heat station housing surrounding at leastportion of said one end of said enclosure and defining with the externalwalls of said enclosure annular passage means and a substantiallycircular passage at the end of said enclosure in fluid communicationwith said annular passage means;

b. fluid communication means between said heat storage means and saidsubstantially circular passage; and

c. a plurality of fluid ports in said enclosure wall providing fluidcommunication between said annular passage means and said expansionchamber.

10. A cryogenic device in accordance with claim 9 wherein said annularpassage means comprises a plurality of concentric annular passages influid communication with each other.

1 l. A cryogenic apparatus in accordance with claim 9 wherein said heatstation housing comprises an annular stainless steel ring, a stainlesssteel sleeve and a copper plate joined in fluidtight relationship.

12. A cryogenic apparatus in accordance with claim 9 wherein saidannular passage means and said circular passage substantially surroundthat portion of said wall which defines said chamber at maximum volume.

13. A cryogenic apparatus, comprising in combination a. a cryogenicmultistage refrigerator, in each stage of which is a movable memberdefining within one end of a cylindrical enclosure a chamber of variablevolume and in which a high pressure expansible fluid is introducedthrough fluid flow path means into each of said chambers to be expandedand then discharged through said flow path means. said flow path meansincorporating heat storage means as an integral part thereof;

. separate heat station means associated with each of said chambers andforming an integral part of said flow path means, each of said heatstation means comprising in combination I. a heat station housingsurrounding at least a portion of said one end of said enclosure anddefining with the external walls of said enclosure narrow fluid passagemeans, and

2. fluid communication means between said heat storage means and saidnarrow fluid passage means and between said narrow fluid passage meansand said chamber with which said heat station means are associated.

14. A cryogenic apparatus in accordance with claim l3 wherein saidnarrow fluid passage means comprise annular passage means surroundingeach of said enclosures and passage means essentially corresponding tothe bottom portion of said external wall of each of said enclosures.

15. A cryogenic apparatus in accordance with claim 13 including heatexchange means associated with each of said heat stations means andadapted to effect indirect heat exchange with a fluid circulatingthrough said heat exchange means.

16. An apparatus in accordance with claim 15 wherein said heat exchangemeans are integral parts of a Joule-Thomson loop.

1. In a cryogenic apparatus in which a refrigerating chamber of variablevolume is defined within a fluid tight enclosure housing and is in fluidcommunication with a fluid flow path in which a fluid stream iscirculated, a heat station adapted to effect indirect heat transferbetween at least a portion of said fluid stream circulating in saidfluid flow path and an external load and comprising means external ofsaid enclosure housing defining narrow fluid passage means around atleast a portion of said refrigerating chamber, said narrow fluid passagemeans within said heat station providing fluid communication betweensaid fluid flow path and said refrigeraTing chamber.
 2. fluidcommunication means between said heat storage means and said narrowfluid passage means and between said narrow fluid passage means and saidchamber with which said heat station means are associated.
 2. Acryogenic apparatus in accordance with claim 1 wherein said narrow fluidpassage means comprises a fluid passage associated with the end of saidenclosure housing.
 3. A cryogenic apparatus in accordance with claim 1wherein said narrow fluid passage means comprises at least one annularpassage around said enclosure housing.
 4. A cryogenic apparatus inaccordance with claim 1 wherein said narrow fluid passage meanscomprises a fluid passage associated with the end of said enclosurehousing and a plurality of concentric connected fluid passages aroundthe side of said enclosure housing.
 5. A cryogenic apparatus inaccordance with claim 1 further characterized by having fluidcommunication means providing a direct fluid connection between saidfluid flow path and said refrigeration chamber and having fluid flowcontrol means.
 6. A cryogenic apparatus in which a movable memberdefines within an enclosure a chamber of variable volume and in which ahigh pressure expansible fluid is introduced through a fluid flow pathinto said chamber and then discharged into a low pressure reservoirthrough said flow path, said flow path incorporating heat storage meansas an integral part thereof; said flow path being characterized asincluding heat station means comprising means external of said enclosuredefining narrow fluid passage means around at least a portion of saidrefrigerating chamber, said narrow fluid passage means providing atleast a portion of a fluid connection between said heat storage meansand said refrigeration chamber.
 7. A cryogenic apparatus in accordancewith claim 5 wherein said heat storage means is located within saidmovable member.
 8. A cryogenic apparatus in accordance with claim 7further characterized by having a fluid channel incorporating checkvalve means adapted to provide direct fluid communication between saidheat storage means and said chamber for high pressure fluid enteringsaid chamber.
 9. A cryogenic apparatus in which a movable member defineswithin one end of a cylindrical enclosure a chamber of variable volumeand in which a high pressure expansible fluid is introduced through afluid flow path into said chamber to be expanded and then dischargedthrough said flow path, said flow path incorporating heat storage meansas an integral part thereof, and including heat station means, said heatstation means comprising in combination a. a heat station housingsurrounding at least portion of said one end of said enclosure anddefining with the external walls of said enclosure annular passage meansand a substantially circular passage at the end of said enclosure influid communication with said annular passage means; b. fluidcommunication means between said heat storage means and saidsubstantially circular passage; and c. a plurality of fluid ports insaid enclosure wall providing fluid communication between said annularpassage means and said expansion chamber.
 10. A cryogenic device inaccordance with claim 9 wherein said annular passage means comprises aplurality of concentric annular passages in fluid communication witheach other.
 11. A cryogenic apparatus in accordance with claim 9 whereinsaid heat station housing comprises an annular stainless steel ring, astainless steel sleeve and a copper plate joined in fluidtightrelationship.
 12. A cryogenic apparatus in accordance with claim 9wherein said annular passage means and said circular passagesubstantially surround that portion of said wall which defines saidchamber at maximum volume.
 13. A cryogenic apparatus, comprising incombination a. a cryogenic multistage refrigerator, in each stage ofwhich is a movable member defining within one end of a cylindricalenclosure a chamber of variable volume and in which a high pressureexpansible fluid is introduced through fluid flow path means into eachof said chambers to be expanded and then discharged through said flowpath means, said flow path means incorporating heat Storage means as anintegral part thereof; b. separate heat station means associated witheach of said chambers and forming an integral part of said flow pathmeans, each of said heat station means comprising in combination
 14. Acryogenic apparatus in accordance with claim 13 wherein said narrowfluid passage means comprise annular passage means surrounding each ofsaid enclosures and passage means essentially corresponding to thebottom portion of said external wall of each of said enclosures.
 15. Acryogenic apparatus in accordance with claim 13 including heat exchangemeans associated with each of said heat stations means and adapted toeffect indirect heat exchange with a fluid circulating through said heatexchange means.
 16. An apparatus in accordance with claim 15 whereinsaid heat exchange means are integral parts of a Joule-Thomson loop.